1. Field of the Invention
This invention relates in general to subsea well equipment, and in particular to a tieback adapter for use if tieback threads in a casing hanger become damaged.
2. Description of the Prior Art
A tieback system is employed for some subsea well drilling and production operations. In a tieback system, the subsea well has a wellhead housing with multiple strings of casing supported in the wellhead housing. Each string of casing is supported by a casing hanger. An annular casing hanger seal seals between each casing hanger and the bore of the wellhead housing.
The tieback system uses a tieback member or adapter for each casing hanger. The tieback adapter is lowered on a tieback conduit, or casing, from the surface platform. The tieback member normally engages tieback threads which are formed in the interior or bowl of the casing hanger. The casing hanger has a sealing surface located in the bowl usually below the tieback threads. The tieback member engages the threads and has a lower end with seals for engaging the sealing surface.
If the tieback threads in the casing hanger become damaged, the tieback threads of the tieback member will not be able to engage the tieback threads to lock the tieback member down. It may be necessary in that event to use a much more expensive system.